This invention relates to method and apparatus for making vitreous silica. Vitreous silica is a non-crystalline form of silicon dioxide, that is, not a quartz crystal, though sometimes referred to as glassy quartz.
The subject of vitreous silica is discussed extensively in the Encyclopedia of Chemical Technology, 2nd Ed. Vol. 18 by Kirk-Othmer at pages 73-105. Various types of silica glasses are discussed in the article Properties and Structure of Vitreous Silica by R. Bruckner in Journal of Non-Crystalline Solids 5(1970) 123-175. This article identifies four types of silica glasses by the manner in which they are produced and also refers to a fifth type produced in a plasma flame.
The vitreous silica produced by the prior art processes and apparatus suffer from various disadvantages, primarily that of purity. Impurities in the range of 25 to 100 parts per million are present in the prior art products. It is an object of the present invention to provide a method and apparatus for producing bubble free vitreous silica the purity of which is limited only by that of the input materials.